Assessment of the efficiency of solar radiation concentrating system.

Abstract

A Solar Radiation Concentrating System for generation of high temperature heat for a solar oven was developed and evaluated at the University of KwaZulu-Natal, Westville Campus, Durban - South Africa. The system concentrates direct solar radiation on a small area receiver which absorbs the radiation and converts it into thermal energy that may be stored and used for several applications where food preparation and water pasteurization is the priority. The concentrator, area 2.2 m², is a half satellite communication dish covered with trapezoidal acrylic mirror tiles. The receiver/absorber is a spiral coil of blackened stainless steel pipe. Oil is circulated as heat transfer fluid. To determine the optimal dimension and position of the receiver, two experimental methods were used: (1) The tiles were scanned using a vertical, self adjusting laser beam to get a distribution of reflected radiation across the focal volume. (2) A thin, blackened stainless steel plate was placed at appropriate distances in the focal volume, and temperature distribution scanned using a temperature gun. The latter method proved to be the more useful. Results of the analysis of system performance showed that the system has the capability to produce high temperatures for domestic purposes. The efficiency of the system is about 35 %.